Recently I have had the pleasure of upgrading a Magento e-commerce store from 188.8.131.52 CE to 1.4.2 CE. The upgrade itself was fairly straightforward as I have upgrading since 1.1 or so. Annoyingly there have been a multitude of irksome errors once the store was upgraded. Here is my list of items to check before you release the upgraded store onto your faithful customers.
- The template system was changed so any custom template from prior to 1.4 required several changes. To regain access to the admin side of the site follow Dmitriy's comment here and remove the folder located at app/code/core/Zend/Cache folder.
- Following Mike's advice at the Noam Design blog resolved the intoHTML error that was being shown by Magento rather than the blog homepage. http://www.noamdesign.com/blog/upgrading-to-magento-1-4/ Follow the steps under "Upgrading Your Existing Theme (modern or else). This discussion on the Magento board also helped me sort through issues with my theme. http://www.magentocommerce.com/boards/viewthread/195616/P45/
- Make sure your Shopping Cart processes credit card orders, a wonderfully nasty issue that thankfully is easily resolved. You need to modify page.xml located at app/design/frontend/blank/Your Theme/layout/page.xml and follow the modification at the following link. http://www.learnmagento.org/magento-bug-fixes/checkout-doesnt-work-on-magento-1-4-x/
- Make sure your USPS shipping options work. They released a new API which caught me by surprise. This is important regardless of the upgrade. http://www.magentocommerce.com/boards/viewthread/215963/P15/
- PayPal Web Payments Standard needs to be changed from Authorize to Sale in the drop down for payments to process correctly.
- IPN must be enabled within Paypal and the address should be set as http://yourwebsite.com/paypal/standard/ipn/
- Reindex all of your data, System->Index Management and Refresh your Cache. System->Cache Mangement.
Good luck to all those sticking with Magento CE. I hope that a fork of the project appears soon so that upgrades will actually be tested by the community rather than Varien. I am still impressed at the product. Heres to a successful upgrade to 1.4.2 on the way to 1.5.